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mukul975
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Complete skill folder anatomy across all cybersecurity skills: - scripts/agent.py: 80-150 line Python agents using real libraries (impacket, boto3, azure-mgmt-*, kubernetes, pefile, yara, scapy, shodan, stix2, etc.) - references/api-reference.md: real API documentation with method signatures - LICENSE: MIT license for all skill folders
62 lines
1.6 KiB
Markdown
62 lines
1.6 KiB
Markdown
# API Reference: Performing DNS Tunneling Detection
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## scapy (DNS Packet Analysis)
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```python
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from scapy.all import rdpcap, DNS, DNSQR, DNSRR, sniff
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# Read from PCAP
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packets = rdpcap("traffic.pcap")
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for pkt in packets:
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if pkt.haslayer(DNSQR):
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qname = pkt[DNSQR].qname.decode()
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qtype = pkt[DNSQR].qtype # 1=A, 16=TXT, 28=AAAA
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# Live capture
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def dns_callback(pkt):
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if pkt.haslayer(DNSQR):
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print(pkt[DNSQR].qname)
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sniff(filter="udp port 53", prn=dns_callback, count=100)
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```
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## Shannon Entropy Calculation
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```python
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import math
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from collections import Counter
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def shannon_entropy(data):
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counter = Counter(data)
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length = len(data)
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return -sum((c/length) * math.log2(c/length)
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for c in counter.values())
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# Normal domain: ~2.5-3.5 bits
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# DNS tunnel: ~4.0-5.0 bits
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```
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## DNS Tunneling Indicators
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| Indicator | Threshold | Rationale |
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|-----------|-----------|-----------|
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| Subdomain entropy | > 3.8 | Encoded/encrypted data |
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| Query length | > 50 chars | Payload in subdomain |
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| TXT queries/domain | > 20/hour | Data channel |
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| Unique subdomains | > 50/parent | Encoded sessions |
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| Digit ratio | > 0.4 | Base64/hex encoding |
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## Common DNS Tunnel Tools
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| Tool | Encoding | Record Types |
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|------|----------|-------------|
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| iodine | Base128 | NULL, TXT, CNAME |
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| dnscat2 | Hex/CNAME | TXT, MX, CNAME |
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| dns2tcp | Base64 | TXT, KEY |
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### References
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- scapy: https://scapy.readthedocs.io/en/latest/
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- DNS tunneling detection: https://www.sans.org/white-papers/dns-tunneling/
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- iodine: https://github.com/yarrick/iodine
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